Induced abortion and subsequent pregnancy duration

Objective: To examine whether induced abortion influences subsequent pregna ncy duration. Methods: Women who had their first pregnancies during 1980, 1981, and 1982 were identified in three Danish national registries. A total of 15,727 wome n whose pregnancies were terminated by first-trimester induced abortions we re compared with 46,026 whose pregnancies were not terminated by induced ab ortions. All subsequent pregnancies until 1994 were identified by register linkage. Results: Preterm and post-term singleton live births were more frequent in women with one, two, or more previous induced abortions. After adjusting fo r potential confounders and stratifying by gravidity, the odds ratios of pr eterm singleton live births in women with one, two, or more previous induce d abortions were 1.89 (95% confidence interval [CI] 1.70, 2.11), 2.66 (95% CI 2.09, 3.37), and 2.03 (95% CI 1.29, 3.19), respectively. Odds ratios of post-term singleton live births in women with one, two, or more previous in duced abortions were 1.34 (95% CI 1.24, 1.44), 1.50 (95% CI 1.26, 1.78), an d 1.58 (95% CI 1.09, 2.28), respectively. Conclusion: The study showed an increase in preterm and post-term pregnanci es after induced abortions. The risk of post-term delivery was high regardl ess of the interpregnancy interval, whereas increased risk of preterm deliv ery was seen mainly when interpregnancy intervals were longer than 12 month s. (Obstet Gynecol 1999;94:948-53. (C) 1999 by The American College of Obst etricians and Gynecologists.).